import java.util.Map; 
import java.util.concurrent.ConcurrentHashMap; 

public class JI9058107 {

	public static void main(String[] args) {
		  Map<String, String> map = new ConcurrentHashMap<>(); 
	        map.put("1", "1"); 
	        map.put("2", "2"); 

	        printMap(map); 

	        map.computeIfPresent("1", (s, s2) -> { 
	            map.computeIfPresent("1", (s1, s21) -> null); 
	            return null; 
	        }); 

	        printMap(map); 
	    } 
	    private static void printMap(Map<String, String> map) { 
	        System.out.println("Map size: [" + map.size() + "]"); 
	        for (Map.Entry<String, String> entry : map.entrySet()) { 
	            System.out.println(entry); 
	        }
	    }

}